“My summer internship was more than going into an office environment,” said Will Hodge, SFPUC intern. “It was also exploring and learning about a water system that spans miles and miles and miles.”
On Tuesday, August 6th, members of the Project Management Bureau (PMB) and SFPUC interns toured the Calaveras Dam and Alameda Creek Fishery in Sunol. Three interns working with the Hetchy Capital Improvement Projects (HCIP) group in Moccasin gave a brief overview of the two sites and shared just a few of the accomplishments these projects have achieved.
The day began with a presentation prepared PMB interns assigned to work with project managers at the SFPUC. This was followed by a presentation given by Susan Hou, the Project Manager for the Calaveras Dam Rehabilitation Project. What the interns learned was that the new Calaveras Dam was an $823M, 7.5 year project that has already received eight national and international awards.
“This project was a prime example of sound communication and coordination, where multiple parties came together for a common goal,” said Hodge.
The project originated when the old Calaveras Dam was found to be lacking in seismic reliability since it was only about 1,000 feet from the Calaveras fault. Being the largest local reservoir and consisting of 40% of the local storage, this was not ideal for the success of the Hetch Hetchy system. Because an earthquake would cause the existing dam to sludge 30 feet and result in catastrophic flooding, it was determined that the reservoir would need to be lowered 50 feet as a preventative measure.
In order to restore the capacity of the reservoir, the new Calaveras Dam was built. The reservoir remained operable during construction, since the new dam is downstream of the old one. Nearly all the dirt for the new earth-dam used soil that was on the site already, and that soil was enough to fill Levi’s stadium in Santa Clara 4 times. Along with the new dam, this project included a new intake tower, a 1,500-foot-long L-shaped spillway, and a stilling basin. The new spillway is ungated, so water will go through the spillway instead of going over the dam and damaging it. Even though construction was recently completed, proposals are already being made to increase the dam height for more capacity.
“As interns, seeing the completion of this dam has us excited and anxious to come back and see the teams carry out the expansion,” said SFPUC intern Mason Dambacher. “Additionally, the lunch after touring the dam gave us the opportunity to chat and connect with other interns and PMB staff.”
As part of the Calaveras Dam Rehabilitation Project, the SFPUC constructed a new fish ladder at Alameda Creek Diversion Dam. The tour was led by Project Manager Bryan Dessaure and Resident Engineer Eric Gee. Located in the upstream portion of the facility, there are four fish screens that allow water to enter the diversion dam while the fish continue swimming safely upstream. A debris broom and gate keep large debris from obstructing the screens, and a rotating broom keeps small debris from clogging them. Two large rakes ensure that debris does not accumulate and disrupt the flow of water.
In addition, the ladder includes a fish tracker which uses sensors to monitor the numbers and location of the fish within the system. If any fish or wildlife are stuck in the ladder after the wet season, they must be rescued and safely transported. With the fish ladder, this facility supports the native aquatic wildlife. The interns learned that the facility is powered entirely by photovoltaic solar panels located on site. However, generators are on site for cases where large machinery must be operated. The construction phase on this project is almost completed, however, the operability of the system must be tested, which requires waiting until there is sufficient flow through Alameda Creek.
“The tour gave us some great insight into the work being done at the Calaveras Dam and Alameda Creek fish passage,” said Dambacher. “We were so energized and curious about the dam’s ability to withstand a major earthquake and whether the fish would be able to successfully swim safely up the stream through the Alameda Creek fish passage.”